1. Field of the Invention
The present invention relates to a wiper blade of a wiper device for a vehicle.
2. Description of the Related Art
It is common to use for a wiper device for wiping a curved windshield of a vehicle a so-called tournament-graph type wiper blade that is composed of a rubber blade, a plurality of levers for supporting the rubber blade. The plurality of levers include a primary lever which is rotatably connected to an arm piece of the wiper arm, a pair of secondary levers which are respectively supported by the primary lever at the opposite ends thereof and two pair of yoke levers which are respectively supported by the secondary levers at the opposite ends thereof, thereby supporting the rubber blade at equal intervals. The above-described levers are rotatably connected to one another in the direction perpendicular to the windshield or in the height of the rubber blade. Therefore, the wiper blade has many rotatable joints so that the rubber blade can bend to come into contact with the curved surface of the windshield.
However, the conventional tournament-graph type wiper blade needs many joints, many parts and manufacturing steps. Moreover, the levers stacked in the height of the rubber blade increase the frontal projected area of the wiper blade relative to the air flowing along the windshield when a vehicle runs. Accordingly, the air resistance and the lift of the wiper blade increase as the vehicle speed increases. A large amount of the air resistance necessitates increase of the mechanical strength of the wiper, which increases the size thereof. A large amount of the lift decreases the pressure of the rubber blade on the windshield, lowering the wiper performance.
JP-A-4-129862 proposes a wiper blade which has levers extending on the sides of the rubber blade, thereby preventing increase in the frontal projected area of the wiper blade even if the curvature of the windshield increases. However, this wiper blade has also the above-described tournament-graph type structure and still needs many parts and manufacturing steps in order to apply this wiper blade to an acutely-curved windshield.
If such a tournament-graph type wiper blade is covered with snow or ice, the levers may be stuck with the snow or ice sticking between the levers. Accordingly the wiper blade can not sufficiently bend to come into contact with the windshield.